LimeSurvey is self-described as "the leading open source tool for online surveys," which probably isn't much of an exaggeration. I stumbled upon it on accident, but it apparently has a team of pretty committed developers who tweak it constantly." - DC Tedrow in his blog

We are happy to announce that a new version of LimeSurvey is now available.
This 1.72 release consolidates 4 months of work on the LimeSurvey 1.71
version, with more than 100 bug fixes, a new language (Icelandic,
kindly provided by Jóhann Friðriksson) and dozens of language updates.